[CS] Remove ConstraintGraph::removeEdge

The only caller was `contractEdges`, which would
only call it with constraints from either the
active or inactive list. The implementation can
therefore be replaced by
`ConstraintSystem::retireConstraint`, and
`removeGeneratedConstraint` can also be removed.

Author: hamishknight

lib/Sema/ConstraintGraph.cpp

@@ -1165,8 +1165,8 @@ bool ConstraintGraph::contractEdges() {
         log << "\n";
       }
 
-      // Merge the edges and remove the constraint.
-      removeEdge(constraint);
+      // Merge the edges and retire the constraint.
+      CS.retireConstraint(constraint);
       if (rep1 != rep2)
         CS.mergeEquivalenceClasses(rep1, rep2, /*updateWorkList*/ false);
       didContractEdges = true;
@@ -1175,35 +1175,6 @@ bool ConstraintGraph::contractEdges() {
   return didContractEdges;
 }
 
-void ConstraintGraph::removeEdge(Constraint *constraint) {
-  bool isExistingConstraint = false;
-
-  for (auto &active : CS.ActiveConstraints) {
-    if (&active == constraint) {
-      CS.ActiveConstraints.erase(constraint);
-      isExistingConstraint = true;
-      break;
-    }
-  }
-
-  for (auto &inactive : CS.InactiveConstraints) {
-    if (&inactive == constraint) {
-      CS.InactiveConstraints.erase(constraint);
-      isExistingConstraint = true;
-      break;
-    }
-  }
-
-  if (CS.solverState) {
-    if (isExistingConstraint)
-      CS.solverState->retireConstraint(constraint);
-    else
-      CS.solverState->removeGeneratedConstraint(constraint);
-  }
-
-  removeConstraint(constraint);
-}
-
 void ConstraintGraph::optimize() {
   // Merge equivalence classes until a fixed point is reached.
   while (contractEdges()) {}

lib/Sema/ConstraintGraph.h

@@ -333,10 +333,6 @@ class ConstraintGraph {
   /// classes until a fixed point is reached.
   bool contractEdges();
 
-  /// To support edge contraction, remove a constraint from both the constraint
-  /// graph and its enclosing constraint system.
-  void removeEdge(Constraint *constraint);
-
   /// The constraint system.
   ConstraintSystem &CS;
 

lib/Sema/ConstraintSystem.h

@@ -1928,24 +1928,6 @@ class ConstraintSystem {
       generatedConstraints.push_back(constraint);
     }
 
-    /// Erase given constraint from the list of generated constraints
-    /// along the current solver path. Note that this operation doesn't
-    /// guarantee any ordering of the after it's application.
-    ///
-    /// \param constraint The constraint to erase.
-    void removeGeneratedConstraint(Constraint *constraint) {
-      for (auto *&generated : generatedConstraints) {
-        // When we find the constraint we're erasing, overwrite its
-        // value with the last element in the generated constraints
-        // vector and then pop that element from the vector.
-        if (generated == constraint) {
-          generated = generatedConstraints.back();
-          generatedConstraints.pop_back();
-          return;
-        }
-      }
-    }
-
     /// Register given scope to be tracked by the current solver state,
     /// this helps to make sure that all of the retired/generated constraints
     /// are dealt with correctly when the life time of the scope ends.